Food Chemistry: Carbohydrates
John Rupnow Department of Food Science Food Processing Center University of Nebraska Carbohydrates
. Most of our calories come from carbohydrates
® Institute of Food Technologists 2 Carbohydrates
. Range from • Simple sugars • Complex starch and fiber
® Institute of Food Technologists 3 Functions of Carbohydrates
. Source of energy . Calorie • Amount of heat required to raise l g of water l C
® Institute of Food Technologists 4 How are Calories Measured?
. Cheetos
® Institute of Food Technologists 5 How are Calories Measured?
O2
® Institute of Food Technologists 6 ® Institute of Food Technologists 7 Chemistry of Carbohydrates
. There is a difference between biological and chemical calories
. Polyhydroxy aldehydes and ketones
® Institute of Food Technologists 8 H O Polyhydroxy C H C O H HO C H H C O H H C O H H C O H H ® Institute of Food Technologists 9 H O Polyhydroxy C H C O H HO C H H C O H H C O H H C O H H ® Institute of Food Technologists 10 H O Aldehyde C H C OH HO C H H C OH H C OH H C OH H ® Institute of Food Technologists 11 H O Glucose C H C OH HO C H H C OH H C OH H C OH H ® Institute of Food Technologists 12 H O Galactose C H C OH HO C H H O C H H C OH H C OH H ® Institute of Food Technologists 13 H Fructose H C O H C O H O C H H C O H H C O H H C O H H ® Institute of Food Technologists 14 H Fructose H C O H . Ketone C O H O C H H C O H H C O H H C O H H ® Institute of Food Technologists 15 Determine the Molecular Formula for:
. Glucose . Galactose isomers . Fructose
. C6H12O6
® Institute of Food Technologists 16 H O Glucose C H C OH HO C H H C OH H C OH H C OH H ® Institute of Food Technologists 17 H O Glucose C H C OH HO C H H C OH H C OH H C OH H ® Institute of Food Technologists 18 H O Glucose C H C OH HO C H H C OH H C OH H C OH H ® Institute of Food Technologists 19 H O Glucose C H C OH HO C H H C OH H C O H C OH H H ® Institute of Food Technologists 20 H O H Glucose 1C H 2 C OH 3 HO C H 4 H C OH 5 H C O 6 H C OH H H ® Institute of Food Technologists 21 6 C
. Forms ring structures 5 . Reacts with self C O
4 1 C C
3 2 C C
® Institute of Food Technologists 22 H H C O-H
C O H H H C C H -O H H O-H C C O-H O-H
® Institute of Food Technologists 23 Disacharides
. Sucrose • Glucose – Fructose
. Maltose • Glucose – Glucose
. Lactose • Glucose - Galactose
® Institute of Food Technologists 24 Functions of Mono and Disaccharides in Food Systems
. Energy . Sweetness
® Institute of Food Technologists 25 Sweetness
Fructose 175 Honey 125 Sucrose 100 Glucose 75 Galactose 32 Lactose 10
® Institute of Food Technologists 26 Sweetness
Sucrose Glucose invertase + Fructose
® Institute of Food Technologists 27 Sweetness
Sucrose Glucose 75 invertase + 125 100 Fructose 175
® Institute of Food Technologists 28 Invertase in Foods
® Institute of Food Technologists 29 Invertase in Foods
® Institute of Food Technologists 30 Lactose Intolerance
. Enzyme treated
• Is there a difference in flavor?
® Institute of Food Technologists 31 Lactose (10)
Glucose (75) + Galactose (32) 55
® Institute of Food Technologists 32 High Fructose Corn Syrup
- glu - glu - glu - glu - glu - glu - glu - corn starch amylase
glu - glu glu - glu - glu glu - glu dextrins glucoamylase
glu glu glu glu glu glu glu corn syrup glucose isomerase
fru fru fru fru fru fru fru
® Institute of Food Technologists 33 Functions of Mono and Disaccharides in Food Systems
. Energy . Sweetness . Body and mouth-feel . Bulking Agents . Energy for fermentation
® Institute of Food Technologists 34 Sugar Alcohols
. Non-cariogenic - No fermented by bacteria in mouth . Not completely metabolized in small intestine • Low caloric • Diabetics - lower glycemic response
Sucrose 100 Manitol 70 Sorbitol 70 Xylitol 100
® Institute of Food Technologists 35 Sugar Alcohols
. Manitol • Used as the dust that coats chewing gum where it keeps the gum from absorbing moisture. • Due to its humectant properties (traps water) low hydroscopicity (does not attract moisture from the air).
® Institute of Food Technologists 36 Sugar Alcohols
. Sorbitol • When dissolved in water the crystals need a lot of energy to dissolve. • Take up heat from the surrounding solution • Endothermic • Has a cooling effect
. Sorbitol - sugar free gum
® Institute of Food Technologists 37 Non-nutritive Sweeteners
Sucrose 100 Sacharrine 40,000 Sweet and Low Aspartame 15,000 “Nutrasweet” “Equal” Acesulfame K 10,000 “Sweet – One” Cyclamate 10,000
® Institute of Food Technologists 38 Sucralose
. 3 hydroxyl groups on sucrose are substituted with Cl
. Increases sweetness 600 times
® Institute of Food Technologists 39 Neotame
. Approved 2002
. 30 times sweeter than aspartame
. 7000 – 13000 times sweeter than sucrose
® Institute of Food Technologists 40 Oligosaccharides
. Short chains of monosaccharides
. Raffinose • glu - gal - fruc
. Stachyose • glu - glu - gal - fruc
® Institute of Food Technologists 41 ® Institute of Food Technologists 42 Polysaccharides
. Long chains of glucose
. Amylose • - glu - glu - glu - glu - glu - glu - glu - • 50 to 500 glucose units
® Institute of Food Technologists 43 Polysaccharides
. Amylopectin • Long branched chains of glucose
glu - glu - glu
- glu - glu - glu - glu - glu - glu - glu glu - glu - glu - glu
® Institute of Food Technologists 44 Starch
. Usually a mixture of amylose and amylopectin
® Institute of Food Technologists 45 Amylase
. Breaks bonds connecting glucose units
® Institute of Food Technologists 46 Cellulose
. Long straight chains of glucose
. Animals do not have the enzyme necessary to break the bonds between the glucose molecules
® Institute of Food Technologists 47 Alginate
. Long chains of negatively charged monosaccharides
® Institute of Food Technologists 48 Alginate
® Institute of Food Technologists 49 Alginate
Na +
Na +
® Institute of Food Technologists 50 Alginate
+Ca +
+ Ca +
® Institute of Food Technologists 51 ® Institute of Food Technologists 52 Polysaccharides in Food Systems
. Starch granule
® Institute of Food Technologists 53 Starch in Water
® Institute of Food Technologists 54 Polysaccharides in Food Systems
. Starch granule
® Institute of Food Technologists 55 H H C O-H
C O H H H C C H -O H H O-H C C O-H O-H
® Institute of Food Technologists 56 H H C O-H
C O H H H C C H -O H H O-H C C + -O-H O-H
® Institute of Food Technologists 57 H H O-H C - +
C O H H H C C + H -O H H - O-H + - C C + + -O-H -O-H
® Institute of Food Technologists 58 O H+
+ H O
® Institute of Food Technologists 59 O H+
+ H O
® Institute of Food Technologists 60 ® Institute of Food Technologists 61 Polysaccharides in Food Systems
. Gelatinization
® Institute of Food Technologists 62 Polysaccharides in Food Systems
. Gelatinization
Starch granule swelling in response to heat
® Institute of Food Technologists 63 Retrogradation
. Reformation of bonds that were broken during heating
® Institute of Food Technologists 64 Syneresis
. Extensive retrogradation • Water is expelled
® Institute of Food Technologists 65 Questions
. Why does bread turn hard?
. Why does microwave soften the bread?
. Why does freezing preserve the softness of bread?
® Institute of Food Technologists 66